Heart rate variability in type 2 spinocerebellar ataxia

Unveiling the role of cerebellar alterations in the autonomic nervous system: a systematic review of autonomic dysfunction in spinocerebellar ataxias

BACKGROUND

Autonomic dysfunctions are prevalent in several cerebellar disorders, but they have not been systematically investigated in spinocerebellar ataxias (SCAs). Studies investigating autonomic deficits in SCAs are fragmented, with each one focusing on different autonomic dysfunctions and different SCA subtypes.

METHODS

Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement, we conducted a systematic review of the literature to assess the presence of autonomic dysfunctions in various SCAs. PubMed served as the primary database, and the Rayyan web application was employed for study screening.

RESULTS

We identified 46 articles investigating at least one autonomic function in patients with SCA. The results were analyzed and categorized based on the genetic subtype of SCA, thereby characterizing the specific autonomic deficits associated with each subtype.

CONCLUSION

This review confirms the presence of autonomic dysfunctions in various genetic subtypes of SCA, underscoring the cerebellum's role in the autonomic nervous system (ANS). It also emphasizes the importance of investigating these functions in clinical practice.

Erythropoietin in Spinocerebellar Ataxia Type 2: Feasibility and Proof-of-Principle Issues from a Randomized Controlled Study

BACKGROUND

Several pieces of evidence have shown the neurotrophic effect of erythropoietin (EPO) and its introduction in the therapeutic practice of neurological diseases. However, its usefulness in the treatment of spinocerebellar ataxia type 2 (SCA2) has not been proven despite the fact that it is endogenously reduced in these patients.

OBJECTIVE

The study aims to investigate the safety, tolerability, and clinical effects of a nasally administered recombinant EPO in SCA2 patients.

METHODS

Thirty-four patients were enrolled in this double-blind, randomized, placebo-controlled, phase I-II clinical trial of the nasally administered human-recombinant EPO (NeuroEPO) for 6 months. The primary outcome was the change in the spinocerebellar ataxia functional index (SCAFI), while other motor, neuropsychological, and oculomotor measures were assessed.

RESULTS

The 6-month changes in SCAFI score were slightly higher in the patients allocated to NeuroEPO treatment than placebo in spite of the important placebo effect observed for this parameter. However, saccade latency was significantly decreased in the NeuroEPO group but not in placebo. The frequency and severity of adverse events were similar between both groups, without evidences of hematopoietic activity of the drug.

CONCLUSIONS

This study demonstrated the safety and tolerability of NeuroEPO in SCA2 patients after 6 months of treatments and suggested a small clinical effect of this drug on motor and cognitive abnormalities, but confirmatory studies are warranted. © 2022 International Parkinson and Movement Disorder Society.

Comparison of Cardiac Autonomic Function in Type 2 Spinocerebellar Ataxia With Normal Control Using Heart Rate Variability as a Tool: A Cross-Sectional Study in Eastern India

BACKGROUND

Spinocerebellar ataxia (SCA) is a disease that refers to a category of inherited ataxias that are characterized by degenerative alterations in the cerebellum, pons, and spinocerebellar tracts. There are several different varieties of SCA and they are classified based on the mutant (altered) gene that causes the disease.

OBJECTIVE

To analyze the cardiovascular autonomic regulation in patients with type-2 spinocerebellar ataxia (SCA-2) from the heart rate variability (HRV) of 20 minutes resting electrocardiogram (ECG) and compare with the age and gender-matched controls.

MATERIALS AND METHODS

HRV of 27 type-2 spinocerebellar ataxia patients was calculated offline from the resting ECG recording and compared with 23 age and gender-matched controls. The HRV was analyzed by HRV software module MLS 310. The frequency and time domain parameters were computed and compared.

RESULT

 Type-2 spinocerebellar ataxia patients have significantly low HRV and parasympathetic activity at rest compared to normal control. The total power in SCA-2 is 13491.63 ± 7660.77 ms2 and the normal control is 21784.76 ± 11008.67 ms2. High-frequency power (HF) which is a marker of parasympathetic activity in SCA-2 is 3823.1 ± 364 ms2 and in normal control is 9006.1 ± 920.64 ms2. The standard deviation of all NN intervals (SDNN), the square root of the mean-squared differences of successive intervals (RMSSD), spectral interval, and delta NN is significantly low in SCA-2.

CONCLUSION

There is decreased parasympathetic tone and low HRV in SCA-2 as compared to normal controls.

Body Mass Index Is Significantly Associated With Disease Severity in Spinocerebellar Ataxia Type 2 Patients

BACKGROUND

Spinocerebellar ataxia type 2 is a progressive neurodegenerative disorder due to an unstable expansion of a CAG repeat in the ATXN2 gene. Although weight loss has been associated with disease progression in several neurodegenerative conditions, it has been barely assessed in patients with spinocerebellar ataxia type 2.

OBJECTIVE

The objective of this study was to test whether body mass index is altered in patients with spinocerebellar ataxia type 2 with varying expansion sizes from early to late disease stages.

METHODS

A cross-sectional case-control study was performed, which included 222 clinically and molecularly diagnosed patients and 214 sex- and age-matched healthy individuals. ATXN2 genotypes and sex were considered as risk factors. Clinical outcomes included the body mass index, age at onset, disease duration, Scale for the Assessment and Rating of Ataxia score, disease stage, dysphagia, and progression rate. Multiple linear regression models were generated.

RESULTS

Body mass index was significantly decreased in male patients, but not in female patients, relative to control subjects. In addition to sex, body mass index was significantly associated with age at onset and progression rate. Conversely, body mass index, along with repeat length in ATXN2 expanded alleles and disease duration, was associated with Scale for the Assessment and Rating of Ataxia score. In addition, body mass index, along with the age at onset and the repeat length in ATXN2 normal and expanded alleles, has a significant influence on progression rate.

CONCLUSIONS

Body mass index might be a useful biomarker of disease severity, particularly in male patients with spinocerebellar ataxia type 2 in the context of nutritional interventions or clinical trials assessing the efficacy of promising new drugs. © 2021 International Parkinson and Movement Disorder Society.

Depressed baroreflex sensitivity from spontaneous oscillations of heart rate and blood pressure in SCA1 and SCA2

OBJECTIVES

To assess the time and frequency domain measures of cardiac autonomic activity/tone in patients of genetically defined spinocerebellar ataxia (SCA) types 1 and 2, as well as to decipher the probable associations among the cardiovascular autonomic parameters and genetic and clinical characteristics.

MATERIALS AND METHODS

Simultaneous 5-min recording of RR interval (RRI) and blood pressure (BP) for the calculation of heart rate variability (HRV), blood pressure variability (BPV) and baroreflex sensitivity (BRS) were performed in genotypically confirmed SCA1 (n = 31) and SCA2 (n = 40) patients and healthy controls (n = 40). Additionally, the International Cooperative Ataxia Rating Scale (ICARS) was used for scoring of clinical severity in SCA patients.

RESULTS

Time and frequency domain parameters of HRV, BPV and BRS were depressed in SCA1 and SCA2 subtypes as compared to controls, although there was no statistically significant difference in autonomic tone between the two SCA subtypes. On correlation analysis, autonomic tone parameters were found to be associated with the clinical and genetic features of the SCA subtypes. Also, ICARS was associated with the genotype (CAG repeat length) in SCA2 patents.

CONCLUSIONS

Cardiac autonomic tone is depressed in both SCA1 and 2 as compared to healthy controls while the two SCA subtypes do not differ in terms of autonomic tone. Also, a typical association exists between disease characteristics and autonomic indices.

Autonomic function testing in spinocerebellar ataxia type 2

PURPOSE

To assess whether autonomic failure belongs to the clinical spectrum of spinocerebellar ataxia type 2 (SCA2), an autosomal dominant genetic disorder showing progressive cerebellar and brainstem dysfunction.

METHODS

We evaluated cardiovascular autonomic function in 8 patients with SCA2 and 16 age- and gender-matched healthy controls. Other autonomic domains were examined through standardized questionnaires and by testing the skin sympathetic reflex.

RESULTS

Patients with SCA2 showed normal responses to cardiovascular autonomic function tests, with the exception of lower baroreflex sensitivity upon standing compared to controls. In questionnaires, 7 out of 8 patients reported bladder disturbances, while 3 out of 6 tested patients had no skin sympathetic reflex.

CONCLUSIONS

We did not observe clinically overt cardiovascular autonomic failure in patients with SCA2. Other autonomic domains (i.e., bladder and sudomotor function) may be affected in the disease.

Spinocerebellar Ataxia Type 2: Clinicogenetic Aspects, Mechanistic Insights, and Management Approaches

Spinocerebellar ataxia type 2 (SCA2) is an autosomal dominant cerebellar ataxia that occurs as a consequence of abnormal CAG expansions in the ATXN2 gene. Progressive clinical features result from the neurodegeneration of cerebellum and extra-cerebellar structures including the pons, the basal ganglia, and the cerebral cortex. Clinical, electrophysiological, and imaging approaches have been used to characterize the natural history of the disease, allowing its classification into four distinct stages, with special emphasis on the prodromal stage, which is characterized by a plethora of motor and non-motor features. Neuropathological investigations of brain tissue from SCA2 patients reveal a widespread involvement of multiple brain systems, mainly cerebellar and brainstem systems. Recent findings linking ataxin-2 intermediate expansions to other neurodegenerative diseases such as amyotrophic lateral sclerosis have provided insights into the ataxin-2-related toxicity mechanism in neurodegenerative diseases and have raised new ethical challenges to molecular predictive diagnosis of SCA2. No effective neuroprotective therapies are currently available for SCA2 patients, but some therapeutic options such as neurorehabilitation and some emerging neuroprotective drugs have shown palliative benefits.

Body Mass Index Decline Is Related to Spinocerebellar Ataxia Disease Progression

Background

Spinocerebellar ataxias (SCAs) are dominantly inherited, progressive ataxia disorders. Disease progression could be preceded by weight loss.

Objectives

We aimed to study the course of weight loss in patients who had the most common SCAs (SCA1, SCA2 SCA3, and SCA6). Additional objectives were to identify subgroups of weight evolution, to determine the factors influencing these evolutions, and to assess the impact of these evolutions on disease progression.

Methods

In total, 384 patients from the EUROSCA prospective cohort study were analyzed who had SCA1, SCA2, SCA3, or SCA6 and at least 3 measurements of weight. Age was used as a time scale. Clinical outcomes were body mass index (BMI) and the Scale for the Assessment and Rating Ataxia (SARA), with scores ranging from 0 to 40. We used a linear mixed model to analyze the course of BMI and a latent class mixed model to identify subgroup BMI evolution.

Results

Overall, BMI declined over time (-0.11 ± 0.03 kg/m² per decade; P = 0.0009). Three subgroups of BMI evolution were identified: "decreasing BMI" (n = 88; 23%), "increasing BMI" (n = 70; 18%) and "stable BMI" (n = 226; 59%). Patients in the decreasing BMI group were more severely affected at baseline with higher SARA scores and a higher frequency of non-ataxia signs (especially motor symptoms) compared with those in the other groups. Weight loss was associated with faster disease progression (5.7 ± 0.7 SARA points per decade; P = 0.036).

Conclusions

The current data have substantial implications for the design of future interventional studies in SCA, as they provide a basis for patient stratification and emphasize the usefulness of BMI as a biomarker for monitoring disease progression.

Comprehensive study of early features in spinocerebellar ataxia 2: delineating the prodromal stage of the disease

The prodromal phase of spinocerebellar ataxias (SCAs) has not been systematically studied. Main findings come from a homogeneous SCA type 2 (SCA2) population living in Cuba. The aim of this study was to characterize extensively the prodromal phase of SCA2 by several approaches. Thirty-seven non-ataxic SCA2 mutation carriers and its age- and sex-matched controls underwent clinical assessments, including standardized neurological exam, structured interviews and clinical scales, and looking for somatic and autonomic features, as well as a neuropsychological battery, antisaccadic recordings, and MRI scans. Main clinical somatic features of non-ataxic mutation carriers were cramps, sensory symptoms, sleep disorders, and hyperreflexia, whereas predominating autonomic symptoms were pollakiuria/nocturia, constipation, and frequent throat clearing. Cognitive impairments included early deficits of executive functions and visual memory, suggesting the involvement of cerebro-cerebellar-cerebral loops and/or reduced cholinergic basal forebrain input to the cortex. Antisaccadic task revealed impaired oculomotor inhibitory control but preserved ability for error correction. Cognitive and antisaccadic deficits were higher as carriers were closer to the estimated onset of ataxia, whereas higher Scale for the Assessment and Rating of Ataxia (SARA) scores were associated most notably to vermis atrophy. The recognition of early features of SCA2 offers novel insights into the prodromal phase and physiopathological base of the disease, allowing the assessment of its progression and the efficacy of treatments, in particular at early phases when therapeutical options should be most effective.

Massive expansion of SCA2 with autonomic dysfunction, retinitis pigmentosa, and infantile spasms

OBJECTIVE

To provide clinical data on a cohort of 6 patients with massive expansion (>200 CAG repeats) of spinocerebellar ataxia type 2 (SCA2) and investigate possible pathways of pathogenesis using bioinformatics analysis of ATXN2 networks.

METHODS

We present data on 6 patients with massive expansion of SCA2 who presented in infancy with variable combinations of hypotonia, global developmental delay, infantile spasms, and retinitis pigmentosa. ATXN2 is known to interact with a network of synaptic proteins. To investigate pathways of pathogenesis, we performed bioinformatics analysis on ATXN2 combined with known genes associated with infantile spasms, retinitis pigmentosa, and synaptic function.

RESULTS

All patients had a progressive encephalopathy with autonomic dysfunction, 4 had retinitis pigmentosa, and 3 had infantile spasms. The bioinformatics analysis led to several interesting findings. First, an interaction between ATXN2 and SYNJ1 may account for the development of retinitis pigmentosa. Second, dysfunction of postsynaptic vesicle endocytosis may be important in children with this progressive encephalopathy. Infantile spasms may be associated with interactions between ATXN2 and the postsynaptic structural proteins MAGI2 and SPTAN1.

CONCLUSIONS

Severe phenotype in children with massive expansion of SCA2 may be due to a functional deficit in protein networks in the postsynapse, specifically involving vesicle endocytosis.